The proposed project aims to examine physical activity behavior in persons with type 2 diabetes mellitus (T2DM) by modeling how self-efficacy, self-regulation and cognitive function impact physical activity behavior over time. The goal is to elucidate psychosocial determinants and mechanisms of physical activity behaviors in the specified population. Secondly, the project will test the effectiveness of a home-based exercise program coupled with a behavior change intervention based in Social Cognitive Theory (SCT; Bandura, 2004). Epidemiological evidence indicate that persons affected by T2DM have extremely low rates of exercise adherence despite the fact that physical activity is considered a first line treatment that can significantly improve disease course. This proposal will examine mechanisms of physical activity adherence in the target population from a neuroscience and social cognitive perspective. It is hypothesized that self-regulatory strategy use, which could be argued to include cognitive control, will indirectly influence physical activity behavior through self-efficacy. As cognitive impairments related to glucose dysregulation may interfere with the ability to successfully maneuver challenges required for self-regulation and behavioral adherence, it is hypothesized that a physical activity intervention specifically focusing on self- regulatory strategies and self-efficacy enhancement may be effective to improve adherence and, secondarily, metabolic health parameters. Additionally, it is hypothesized that participation in the four week, specifically designed physical activity behavior change intervention will improve physical activity behavior in individuals with T2DM compared to a usual care group, and that observed differences will be sustained for a six month follow-up. Recruitment will include 80 men and women (ages 40-70 years) with diagnosed T2DM from east central Illinois who will be randomly assigned into the intervention or usual care group. Intervention participants will meet several times, within 1 month of beginning the intervention, in group workshops where a social-cognitive based exercise behavior intervention curriculum will be delivered. Intervention participants will be taught and encouraged to regularly track at home activity. Measures will include physical activity behavior (via accelerometry); fasting blood glucose; self-efficacy; self-regulatory strategy use, which include self-monitoring and goal-setting; and cognitive function. Measures will be taken at baseline, m1, and m7. Improving exercise adherence in this specific population promises significant health improvement and would lessen individual and society health burdens. The proposed project will deepen understanding concerning mechanisms of physical activity adherence in the target population.